Polyamide resins are used in a wide range of fields such as electric parts, electronic parts, and automobile parts due to excellent properties thereof in terms of heat resistance, abrasion resistance, chemical resistance and flame retardancy.
Particularly, in the automobile industry, metal parts are being replaced with plastic parts in order to achieve weight reduction. In particular, peripheral parts of an engine compartment are exposed to a high temperature environment for a long time and thus are manufactured using polyamide resin compositions having excellent heat resistance.
As smaller engines are becoming more popular in the automobile industry, the number of automobiles employing a turbocharger is increasing to reduce fuel consumption. In an automobile employing a turbocharger, the temperature in the engine compartment rises greatly due to high output power. Thus, there has been a need to use a material having a higher level of heat resistance for parts in the engine compartment such that the parts can withstand a high temperature environment for a long time.
Generally, organic antioxidants such as phenol or phosphite-based antioxidants are widely used in order to secure high long-term heat stability of a polyamide resin composition. However, there is a limitation in maintaining excellent physical properties at high temperatures over a long period of time.
Copper halide heat stabilizers such as a CuI/KI mixture, which is known to have excellent long-term heat stability at high temperature as compared with organic antioxidants, have been used. However, copper is likely to discolor or precipitate over time, causing problems when used in electrical, electronic and automotive parts.
Therefore, there is a need for a polyamide resin composition which can retain high heat stability even when exposed to high temperature for a long time so as to be used for peripheral components of an engine room in an engine compartment of an automobile.